Many communication systems use Internet Protocol (IP) to transport packet data representative of voice, video, data or control traffic between endpoints (or “hosts” in IP terminology). In such systems, the data is divided into IP packets called datagrams that include addressing information (e.g., source and destination addresses) that enables various routers forming an IP network to route the packets to the specified destination. The destination address may comprise a unicast address identifying a particular host or a multicast address shared by a group of hosts. Typically, the hosts include various fixed devices and mobile wireless devices, often called mobile nodes, that are capable of roaming from site to site or even between different communication networks that use IP.
As wireless communication and mobile internet access have grown in popularity, it is envisioned that multiple IP-addressable devices will be carried within a car, airplane, train or even on a person. Such a collection of devices is known as a mobile network and the IP-addressable devices residing within the mobile network are known as mobile network nodes. Further, it is envisioned that certain mobile network nodes will periodically detached from a mobile network, thereby becoming independent mobile nodes. This may occur, for example, when a mobile wireless device carried by a policeman (i.e., forming part of a mobile network when carried within a police vehicle) becomes an independent mobile node when the device is removed from the vehicle. A need has arisen to provide for IP mobility of the mobile network as well as mobile network nodes detachable from the mobile network, that is to maintain IP connectivity for the mobile network and for any mobile network nodes that are detached from the mobile network as it (and they) may move from site to site.
The most recent IP standard, Internet Protocol version 6, called “IPv6,” supports IP mobility for individual mobile nodes (presently defined in “draft-ietf-mobileip-ipv6-14.txt”) but does not address mobile networks or the special case of mobile nodes having detached from mobile networks. Generally, mobile IPv6 provides for a mobile node to move to different sites or networks without changing its IP address. A mobile node is always addressable by its “home” IP unicast address associated with a home site or network, regardless of the node's current point of attachment to the network infrastructure. While situated away from its home network, the mobile node is also associated with a forwarding address known as a “care of” address. The mobile node is addressable either directly by the care of address or indirectly by the home address. In the latter case, the IPv6 protocol causes packets addressed to the home address to be intercepted by a “home agent” and tunneled to the care of address.
To that end, mobile IPv6 relies upon individual mobile nodes performing mobility management, i.e., recognizing when they are at a foreign site and, in such case, to inform their home agent of their new care of address. This is accomplished by messages termed “binding updates.” Mobile nodes may also send binding updates to various devices (termed “correspondent nodes”) corresponding (or prospectively corresponding) with the mobile nodes. In such case, the mobile node maintains a binding list identifying which correspondent nodes should receive binding updates.
A problem that arises is that, in the case of mobile networks, it is generally undesirable to place all mobility management responsibility in the mobile network nodes because the mobile nodes, while attached to the mobile network, appear from their point of view to be stationary and may be unaware of movements of the mobile network within the external network. Consequently, it is impractical to burden mobile network nodes with the responsibility to detect movement of the mobile network. Moreover, if one were to place all mobility management in the mobile nodes, binding update “storms” may result upon multiple mobile network nodes simultaneously sending binding update messages each time the mobile network moved to a new site or network. As will be appreciated, binding update storms create network traffic overhead that can adversely affect handoff times and quality of service of the network.
To address this problem, related patent application Ser. No. 09/993,255 provides a method and apparatus whereby mobility management responsibility for a mobile network is placed entirely in a mobile router on behalf of its attached mobile network nodes. In such manner, the mobile router, rather than mobile nodes, detects movement of the mobile network and sends any required binding updates to home agents and correspondent nodes. A problem with this approach, however, is that if and when a mobile network node detaches from the mobile network and roams to another mobile network or fixed network (and hence must perform mobility management on its own behalf), the mobile network node will not know which correspondent nodes to send binding updates to because it will not have performed any mobility management on its own behalf while attached to the mobile network and thus will not have maintained a binding list.
Accordingly, there is a need for a method and apparatus for providing IP mobility for mobile networks that better supports IP mobility for detachable mobile nodes of the mobile network. Advantageously, the method and apparatus will place the majority of mobility management responsibility in a mobile router so as to reduce or eliminate the likelihood of binding update storms and so that mobile network nodes, while attached to the mobile router, need not be aware of movement of the mobile network, yet place enough mobility management responsibility to mobile nodes, on their own behalf, to facilitate their ability to perform mobility management when detached from the mobile router. The present invention is directed to satisfying these needs.